A switching controller for systems with hard uncertainties

A novel control scheme is proposed to solve the problem of stabilizing nonlinear uncertain systems with an unknown sign of the control gain and potentially unbounded nonlinearities. If the drift term f(x) has a growth rate such that the overall system has a finite escape time t^*, only a guess of a lowerbound, different from zero, of t^* is necessary to design the control law. In spite of the hard uncertainties which affect the system model, the proposed switching controller is capable of asymptotically stabilizing the origin of the state space. The properties of the proposed control algorithm are compared with those of a well-known adaptive-control procedure when applied to the same class of systems.